1. Field
The present disclosure relates generally to aircraft and, in particular, to a method and apparatus for operating an aircraft. Still more particularly, the present disclosure relates to a method and apparatus for compensating for pitch angles during maneuvering of an aircraft.
2. Background
During operation, an aircraft may fly in the air as a result of an aerodynamic force called lift. Lift is generated by the wings of an aircraft as air flows past the wings as a result of forward movement of the aircraft. The wings of an aircraft generate lift because of a pressure reduction on the upper side of the wings. The lower pressure on the upper side of a wing combined with a higher pressure on the underside of the wing provides the lift. Lift may be increased by increasing the angle of the wing cord relative to the airflow. This angle is also referred to as the angle of attack.
When an aircraft performs a turn, the roll angle increases and the lift vector follows the roll for the turn, decreasing the lift in the vertical direction. With decreased lift in the vertical direction, the aircraft also may change altitude. These changes in the movement of the aircraft are often undesirable during a turn. Instead, it is desirable to substantially maintain the altitude of the aircraft during the turn.
Currently available control systems for aircraft use a versine function and a polynomial function of air pressure or dynamic pressure to compensate for a pitch angle or angle of attack that may cause the aircraft to stay at the same altitude during a turn. These functions may be inaccurate for roll angles above 30 degrees.
Therefore, it would be advantageous to have a method and apparatus that takes into account one or more of the issues described above, as well as possibly other issues.